1. Field of the Invention
This invention relates generally to the field of computer systems and more specifically to a method and apparatus for enabling computer subsystems to function with various processors having different clocking schemes, without the need to implement hardware modifications to the computer subsystem.
2. Background of the Invention
Computer technology product development cycles are shrinking at a rapid rate. Advancements in function and improvements in speed of computer processing systems occur so rapidly that computer technology products are only on the market for a short time period before being rendered obsolete by products with greater functional capabilities and faster processing speeds. As a result, manufacturers of computer processing systems have only a short period of time to recoup design and manufacturing costs.
Computer processing systems frequently include a motherboard. Typically, a motherboard is a printed circuit board (PCB), which is formed from a flat board made of nonconducting material, such as plastic or fiberglass. Typically, a microprocessor chip, other special function chips (such as a math co-processor, memory cache, or graphic accelerator), main memory, support circuitry, I/O bus, CPU bus, bus controllers and connectors are mounted on a motherboard. A common method for mounting a microprocessor onto a motherboard includes physically inserting the microprocessor into a socket or connector attached to the motherboard. The microprocessor is connected to the other elements in the computer processing system via conductors that are printed on the motherboard. Another common method of mounting microprocessors on a motherboard includes soldering the microprocessor chip into holes in the motherboard wherein the holes have been predrilled to hold the pins on the chip. Alternatively, another method includes soldering the microprocessor chip directly to the surface of the motherboard.
Advancements in the capabilities and speeds of computer processing systems are often centered around improved microprocessors. Very-Large-Scale Integration (VLSI) and Large Scale Integration (LSI) engineering techniques allow chip designers to add many complex functions on a single chip. Benefits of including new functions in the microprocessor as opposed to a co-processor or other on-board element include space savings, and, more importantly, faster operating speeds because the processing speeds of the microprocessor are far greater than the communication speeds between elements on the motherboard.
Thus, the microprocessor frequently has to be replaced to provide new functions and faster speeds to a computer processing system. A problem with changing the microprocessor is that it also often requires changes to the other hardware components of the computer processing system on the motherboard (the "subsystem"). The subsystem frequently must be changed to account for differences in the clocking schemes and pin and package configurations of the different processors. Thus subsystem designers must implement a unique subsystem design for each new processor. Such redesign efforts represent large expenditures of time and money.
What is needed is a common interface that will eliminate the difference at the subsystem level between various processors, so that a single hardware subsystem printed circuit board design can support various microprocessors without making changes to the subsystem. A common interface of this type will allow manufacturers to reuse a subsystem design over multiple generation of processors, thereby increasing the time period the subsystem remains a competitive product in the marketplace and increasing the chance that the manufacturer recovers its design expenses related to the subsystem.